Hepatitis B virus (HBV) encoded X protein (HBx) has been implicated in apoptotic
and related pathogenic events during hepatocellular carcinoma. However, the underlying molecular mechanism through which HBx acts is largely unclear. We used t
andem affinity purification under mild conditions to gain insight into the HBx interactome in HBV-producing HepG2.2.15 cells
and identified 49 proteins by mass spectrometry that are potentially associated with HBx. Two of the key proteins of the caspase-independent apoptosis pathway were newly identified, apoptosis-inducing factor (AIF)
and the homologous AMID (AIF-homologue mitochondrion-associated inducer of death). We confirmed the interactions of HBx with AIF
and with AMID by reciprocal coimmunoprecipitation experiments, respectively. We observed the expression of HBx-reduced AIF-mediated apoptosis
and HBx colocalization with AIF
and AMID, principally in the cytoplasm. Furthermore, the elevated cytoplasmic levels of HBx could inhibit mitochondrion-to-nucleus translocation of AIF. Here, we present the first detailed molecular evidence that HBx can repress apoptosis via inhibition of the caspase-independent apoptosis pathway. This inhibition of apoptosis involves the repression of the mitochondrion-to-nucleus translocation of AIF, although tests with AMID were not conclusive. These findings provide important insights into the new mechanism of the apoptosis inhibition by HBV.
Keywords:
hepatitis B virus; HBx; AIF; AMID; apoptosis; andem+affinity+purification&qsSearchArea=searchText">tandem affinity purification